Rancho Santiago de Santa Ana was a 63,414-acre (256.63 km2) Spanish land concession in present-day Orange County, California, given by Spanish Alta California Governor José Joaquín de Arrillaga in 1810 to Jose Antonio Yorba and his nephew Pablo Peralta. The grant extended eastward from the Santa Ana River to the Santa Ana Mountains, with a length of more than 22 miles (35 km).
The lands encompass present-day Santa Ana, Orange, Villa Park, Anaheim Hills, El Modena, Tustin, Costa Mesa, and a part of Irvine, which was formerly known as Rancho Lomas de Santiago and was titled to one of the Yorbas.
Juan Pablo Grijalva, a Spanish soldier who traveled to Alta California with the De Anza expedition, was the original petitioner for the lands that became known as the "Rancho Santiago de Santa Ana". He died before the grant was approved and the lands went to his son-in-law, Jose Antonio Yorba and his grandson, Juan Pablo Peralta. On July 1, 1810, land later named Rancho Santiago de Santa Ana was granted to Jose Antonio Yorba and his nephew Pablo Peralta by Governor José Joaquín de Arrillaga on behalf of the Spanish Government. This was the only land grant in present-day Orange County given under Spanish Rule which were rare during this time. This was only two and a half months before the start of the war for Mexican Independence (1810-1821). The surrounding land grants or ranchos were granted by the Mexican government after Mexican independence in 1821.
Jose Antonio Yorba built an elaborate adobe hacienda, El Refugio (the Refuge), located near present-day First and Sullivan Streets in western Santa Ana.
With the Mexican Cession of California to the United States following the Mexican-American War, the 1848 Treaty of Guadalupe Hidalgo provided that the land grants would be honored. As required by the Land Act of 1851, a claim for Rancho Santiago de Santa Ana was filed with the Public Land Commission in 1852, and the grant was patented to Bernardo, Teodoro and Ramón Yorba in 1883.
In 1854, the Yorba family sold Rancho Santiago de Santa Ana to José Antonio Andrés Sepúlveda. Sepúlveda later lost the land due to bankruptcy caused by fighting to uphold his land claims in court. In 1869, William Spurgeon and Ward Bradford purchased 74.27 acres (0.3006 km2) of the ranch to form the city of Santa Ana. It became the seat of government for the County in 1889.